1. Field of the Invention
The present invention relates to a substrate storage container that is employed for storing, accommodating, transporting and feeding substrates such as silicon wafers or glass masks.
2. Related Background Art
Silicon wafers are formed of various sizes in semiconductor factories. More IC chips can be manufactured from a silicon wafer of large diameter than from a silicon wafer of small diameter. For example, whereas only 44 IC chips can be manufactured from a silicon wafer of diameter 200 mm (8 inches), some 112 IC chips can be manufactured from a silicon wafer of diameter 300 mm (12 inches).
In view of the advantage of being able to considerably increase the number of IC chips that can be acquired, silicon wafers of large diameter are being increasingly used. Accompanying this, there is a shift from the conventionally employed open-top box-type substrate storage container to an open-front box-type substrate storage container, in respect of which automation is a precondition.
Although not shown, a substrate storage container for storing silicon wafers of large diameter comprises an open-front box-type container casing, a cover, a front retainer, a sealing gasket and a latch mechanism. The container casing stores a plurality of silicon wafers in a stack. The cover is detachably fitted onto the front aperture of the container casing. The front retainer is mounted on the cover and retains the front periphery of the plurality of silicon wafers. The sealing gasket is interposed between the container casing and the cover. The latch mechanism is incorporated in the cover and fixes the cover that is fitted onto the front aperture of the container casing. In this substrate storage container, insertion/removal of silicon wafers and/or opening/closing of the cover are performed automatically by a special-purpose device (robot or cover opening/closing device).
Such substrate storage containers can be classified into the FOUP type (standardized in accordance with SEMI standard E 47.1) that are employed for substrate feeding in a processing step and FOSB type containers (standardized in accordance with SEMI standard M31) that are employed for shipping or transportation of silicon wafers.
However, there was the problem that, since the mode of opening/closing the cover was different as between the FOUP type and FOSB type, the cover opening/closing device standardized for the FOUP type could not be employed for opening/closing the cover of the FOSB type without modification.
Also in the case of the FOSB type there was a risk of the silicon wafers being damaged since the silicon wafers might be subjected to greater than anticipated shock during transportation (for example changes in air pressure during transportation by air).
Also, in the case of silicon wafers of large diameter, the front and back surfaces of the silicon wafer are both formed as specular surfaces and there are strict standards relating to particles; furthermore, when the silicon wafers are inserted or removed by a special-purpose robot, generation of particles and/or mispositioning must be suppressed to the utmost. Furthermore, the cover may sometimes be subjected to repeated opening/closing operations and in this case there was a risk of mispositioning of the sealing gasket or excessive deformation.